High-energy plastic-bonded explosive

ABSTRACT

A HIGH-ENERGY, PLASTIC-BONDED EXPLOSIVE OF THE NOMINAL COMPOSITION 95 WT. PERCENT HMX, 2.5 WT. PERCENT ESTANE, AND 2.5 WT. PERCENT DNPAF HAVING IMPROVED TEMPERATURE STABILITY AND SIGNILICANTLY BETTER HANDLING SAFETY THAN STANDARD PLASTIC-BONDED EMPLOSIVES.

United States Patent iii-s2 ABSTRACT OF THE DISCLOSURE A high energy,plastic-bonded'explosive of the nominal composition 95 'WtJpercentEHMX,2.5 wt. percent Estane, and; 2.5 percent DNPAF having improvedtemperatur stability and significantly better handling safety thanstandard plastic-bonded explosives.

BACKGROUND OF'THE INVENTION The invention described herein was made inthe course of, or under, a contract with the US. Atomic EnergyCommission. It relates to high explosives and more particularly tohigh-energy, plastic-bonded explosives.

Plastic-bonded explosives represent a class of explosives which can bemade into pressings from which can be fabricated--usually bymachining-desired shapes. These explosives are pressed from so-calledmolding powders which are typically prepared by the slurry technique.Powdered explosive and water are mixed in a kettle equipped with acondenser and agitator. A lacquer composed of the plastic (together witha plasticizer, if necessary) dissolved in a suitable solvent is added tothe slurry. The solvent is removed by distillation, causing the plasticphase to precipitate out on the explosive. The plasticexplosiveagglomerates into beads as the stirring and solvent removal continues.Finally, water is removed from the beads by filtration and drying; theresultant product is the molding powder. The powder is then pressed intoshape by either compression molding with steel dies or hydrostatic orisostatic pressing under vacuum. The pressing may readily be machinedinto a desired shape for actual use.

A well-known and useful high-energy, plastic-bonded explosive is knownas PBX-9404 and has the formulation 94 wt. percent HMX, 3 wt. percent NC(containing 12 wt. percent nitrogen), and 3 wt. percent CEF.Difiiculties associated with PBX-9404 are that its handling safety isnot as good as desired and it lacks suflicient thermal stability for usein certain high-temperature environment.

DEFINITION OF TERMS As used within this application, HMX is an explosivehaving the chemical name 1,3,5,7-tetranitro-1,3,5,7-tetrazacyclooctanealso designated as cyclotetramethylenetetranitramine; Estane is a tradename for a thermoplastic, polyurethane elastorner generally preparedfrom long chain diols and toluene diisocyanate and manufactured by theB. F. Goodrich Co.; DNPAF is a eutectic mixture of the formal and acetalof 2,2-dinitropropanol; NC is nitrocellulose; CEF istris-(fi-chloroethyl) phosphate; DPA is diphenylamine; and PBX meansplastic-bonded explosive.

SUMMARY OF THE INVENTION A plastice-bonded explosive containing 95 wt.percent HMX and having Estane as the plastic bonding agent, and DNPAF asthe plasticizer has an explosive energy comparable to that of PBX-9404but possesses greater temperature stability and significantly betterhandling safety.

Optimum characteristics are exhibited by the composition wt. percentHMX, 2.5 wt. percent Estane, and 2.5 wt. percent DNPAF.

DESCRIPTION OF THE PREFERRED EMBODIMENT The explosive of this inventionis designated as PBX- 9501.

PBX-9501 may readily be prepared in pilot plant quantities using thefollowing slurry process. A lacquer of Estane and DNPAF is prepared bysoaking 397 g. of Estane 5703, F-l in 4.7 l. of 1,2-dichlorethane for a12- hour period, adding 443 g. of DNPAF, and then heating and agitatingthe solution. The DNPAF weight is increased by a factor of 0.115 over2.5 wt. percent to correct for loss of impurities and water solubility.An HMX slurry is prepared by mixing 23.25 lb. of coarse HMX and 10.001b. of fine HMX in 20 gal. of water. The slurry is then heated to 60 C.and 600 ml. of toluene is added. The toluene is used to control theparticle size. It acts as a transient plasticizer and maintains asuflicient tack in the binder during the forming stage to allow theproduction of particles of the desired size. After toluene addition, thelacquer at 50 C. is added to the slurry and the resulting dispersion isheated to 85 C. The dispersion is cooled to 50 C. and filtered and theresulting powder is dried at 60 C. in a forced draft oven. This resultsin 35 1b. of powdered PBX-9501. The powder is then pressed into desiredshape at 20,000 p.s.i. and C. With thr intensifications, over 99% oftheoretical density is obtained.

Table I shows a comparison of the properties of PBX- 9501 and PBX-9404.The handling safety of PBX-9501 is indicated by the skid test data ofTable II. In the skid test, samples are skidded onto sandpaper targetsat a 45 angle from the heights indicated. As used in Table II, Nindicates no detonation and E indicates detonation. The H of 26 ft. andoverpressure of about 0.7 p.s.i. are exceptional for a high-energyplastic-bonded explosive. Other materials in this energy class aremarkedly more sensitive and hazardous. For example, PBX-8404 has an H of4 ft. and an over-pressure of 8 p.s.i. Table III compares thedecomposition rates for the binders of PBX- 9501 and PBX-9404,respectively, at the temperatures indicated. The compound DPA is addedto the PBX-9404 to retard the decomposition of the nitro compoundscontained therein. The PBX-9501 binder does not degradeautocatalytically as does that for PBX-9404 and degrades at a much lowerrate.

TABLE I.PROPERTIES Composition (wt. percent):

HMX 95 94 Estane 2. 6 DNPAF 2. 5 N 3 CEF. 3 Theoretical density(gJcmfi) 1. 855 1. S66 Typical density (glean!) 1. 843 1. 844Cylinder-test comparison at 5 1pm.. 0. 995 1. 000 Cylinder-testcomparison at 19 mm 1. 022 1. 000 Plate-dent comparison ol) 1. 011 1.000 D comparison (Poi) 1. 008 1. 000 Detonation velocity (m./s.) 8, 8268, 782 Vacuum stability (ml./g.- G./48 l1.) 0. 8 3. 5 DTA exotherm C.)240 180 Impact sensitivity (cm., 12/12B 44/80 42/47 Small-Scale gap(inch of brass) 0. 060 0. 097 Minimum priming (mg. Exte 67 24 x) Sparksensitivity (joules, 3-mil Pb foil) TABLE IL-SKID-TEST RESULTS-45SANDPAPER TARGETS PBX-9501 (0.5 wt. percent calcium stearate) PBX-9501Drop Drop he! ht height (ft. Results (ft.) Result 84 V. E E M E .v 32 EE N E N 32 N E E E E 2.26 N E .53. N N l6 N N N N 50? height 25 it.overpressure-0.7 p.s.1. (avg.) 507 hei hi'ft'.Vifsiif fifififj but abliE'Sj11dg6d to be of same magnitude as with calcium stearated version.

thane elastomer prepared by reacting long chain diols with TABLEHI'TESTIMATED TIME FOR 3% DECOMPOSITION toluene diisocyanate, and 2.5wt. percent of a eutectic NC/OEF mixture of the formal and acetal of2,2-dinitropropanol. 0. Estane/DNPAF DPA 15 References Cited UNITEDSTATES PATENTS A I 3,296,041 1/1967 Wright 149--92 X Nam-D1 and vacuumstability results given in Table 8150 3,447,980 6/ 1969 Voight 14992 Xgrei fixilogfgiete the greater thermal stability 0! PBX-9501 as compared20 3,507,722 4/1970 Hamrick X Wha Claim is! STEPHEN I. LECHERT, JR.,Primary Examiner 1. A high-energy, plastic-bonded explosive of thenominal composition 95 wt. percent 1,3,5,7-tetranitro-1,3,5,7- US, Cl.X.R.

tetrazacylooctane, 2.5 wt. percent thermoplastic, polyure- 5 14919, 88

